change ExtendParam to map[string]interface in cce cluster

[ShiChangkuo]

What this PR does / why we need it:
change change ExtendParam to map[string]interface, then we can support parameters of prePaid.

Which issue this PR fixes (optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close that issue when PR gets merged): fixes #

Special notes for your reviewer:

Release note:

[coveralls]

Pull Request Test Coverage Report for Build 1218

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 68.171%

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Totals
Change from base Build 1215:	0.0%
Covered Lines:	11559
Relevant Lines:	16956

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💛 - Coveralls